DE 31 03 632 C2 discloses a process for the production of a cavity floor, in which a form with a profiled, slightly flexible sheet material having a plurality of individual stud-like outward bulges forming supports or legs, is produced on an underfloor and to which is subsequently applied a flooring plaster. The bulges are arranged with reciprocal spacings such that the supports adapt to an uneven contour of the underfloor on applying the flooring plaster, the latter being applied as a fluid suspension. This is intended to bring about an adaptation of the form to uneven underfloors without additional compensating measures such as the placing of small plates under the supports. However, this known process, or the form sheet used for it, suffers from the disadvantages that the reciprocal spacing of the supports is given by the flexibility of the sheet and not the requirements made with regards to the cavity floor. However, this spacing must also be dependent on the maximum unevenness which occurs, i.e. it is much larger than would be necessary in the normal case. Thus, as a result of this provision of a minimum spacing, the sheet is not generally suitable as a form for cavity floors. Due to the relatively large distance between the individual bulges, the sheet must also be very stable and therefore very thick. Apart from a high material expenditure, this constitutes a high fire load in the building if, as is conventionally the case, the sheet is made from flammable plastic.
The problem of the present invention is therefore to improve the known form sheet in such a way that, despite the capacity to adapt to all unevennesses of the underfloor which are likely to occur, the spacing between the bulges can be kept so small that the sheet is usable for all cavity floors and can be relatively thin.